For months, national security experts have warned that the large number of unfilled positions at the State Department risked putting the United States in jeopardy in the event of a crisis. Now, with North Korea threatening war and a new US intelligence finding that Pyongyang has succeeded in miniaturizing a nuclear bomb, a crisis has arrived, and President Donald Trump has yet to name a US ambassador to South Korea.

The personnel gap comes amid confusing signals out of Washington — at a time when one of America’s most important and vulnerable allies is seeking clarity and instruction.

“When managing both a chronic and an acute challenge such as those posed by North Korea, the South Korean government needs someone on the scene who can provide tight alliance consultation on the ground and 24/7,” said Patrick Cronin, an Asia scholar and Republican at the Center for a New American Security, an influential bipartisan think tank. “There is no substitute for an able and trusted ambassador.”

The utility of having a Senate-confirmed diplomat in Seoul is especially important given the penchant of Trump and his secretary of state, Rex Tillerson, to respond in markedly different ways to international events, experts said.

On Tuesday, Trump threatened Pyongyang with “fire and fury like the world has never seen” in off-the-cuff remarks delivered at a New Jersey golf resort. A day later, Tillerson downplayed the likelihood of any immediate conflict. “I think Americans should sleep well at night," Tillerson said while his plane refueled in Guam.

For South Korea, which has thousands of artillery pieces pointed at it from across the North Korean border, the absence of an ambassador is unnerving, particularly given the appointments of envoys in other Asian capitals.

“The South Koreans are wondering why Japan, China, Singapore and other Asian countries have an ambassador in place, but they do not,” said Bonnie Glaser, an Asia scholar at the Center for Strategic and International Studies. “There is no representative of the president in country to ensure smooth communications.”

The State Department, which has been bitterly feuding with the White House over appointments, pointed the finger at 1600 Pennsylvania. “For all presidential nominations we’d refer you to the White House,” a State Department spokesperson told BuzzFeed News, when asked about the slow pace of the appointment.

A White House spokesperson, meanwhile, said “we are not going to comment on personnel decisions that have not yet been announced by the White House.”

In June, unnamed US officials told a South Korean newspaper that Victor Cha, a Korea expert at Georgetown University, was the likely pick, a move widely praised by Asia experts from both parties.

But the absence of any movement on Cha’s nomination and his publication of an op-ed in the Washington Post coauthored by a former policy aide to Hillary Clinton, a perennial punching bag for Trump, has raised concerns about the status of his appointment.

In the column, Cha and Clinton adviser Jake Sullivan outlined a new plan for resolving the North Korea crisis that involves China “paying for North Korea to halt and roll back its nuclear and missile programs.”

“It’s not enough to ask China to pressure Pyongyang to set up a U.S.-North Korea negotiation,” the authors wrote in July. “China has to be a central part of the negotiation, too.”

When asked about his potential appointment, Cha declined to comment.

One person close to the White House said he believed the nomination was a “done deal” and that Cha’s op-ed didn’t bother the Trump administration because it “didn’t say anything bad about Trump.”

Other vacant positions relevant to the North Korean crisis include the assistant secretary of state for East Asian and Pacific Affairs — a job that career official Susan Thornton is performing on an acting basis — and the under secretary of state for Arms Control and International Security.

A similar situation prevails at the Pentagon, where policy toward North Korea is led by the assistant secretary of defense for Asian and Pacific security affairs, a position currently held on an acting basis by David Helvey. He has no deputy on east Asia affairs, as he holds that job as well. Cara Abercombie, the deputy in charge of South and Southeast Asia, is on sabbatical. That leaves Helvey largely on his own in charge of a region that stretches from Afghanistan to New Zealand.

Cronin, the Asia expert, said an ambassador appointment couldn’t come soon enough. “Embassy staff are capable but they lack the political reach of a Senate-confirmed ambassador,” he said. “The military leadership on the ground is also superb, but the commanders in the US-ROK Combined Forces Command require civilian leadership from the White House and the Blue House.”